Simultaneous Realization of Significantly Enhanced Breakdown Strength and Moderately Enhanced Permittivity in Layered PMMA/P(VDF–HFP) Nanocomposites via Inserting an Al2O3/P(VDF–HFP) Layer

Paraelectric/ferroelectric bilayer composites are promising candidates for high-performance dielectric capacitors. However, the energy densities of these composites need to be further improved to satisfy the miniaturization of electronic devices. Herein, an Al2O3/P­(VDF–HFP) buffer layer is inserted between a paraelectric PMMA layer and a ferroelectric P­(VDF–HFP) layer, forming a novel trilayer structure. It is interesting to find that the buffer layer effectively alleviates the huge electric field gap between the P­(VDF–HFP) layer and PMMA layer, yielding substantially improved breakdown strengths (>600 kV/mm), which are over 140% that of the bilayer P­(VDF–HFP)/PMMA composite (∼425 kV/mm). In addition, the introduction of the buffer layer also results in improved interfacial polarization, hence, the moderately elevated permittivity. Consequently, a high energy density of 10.03 J/cm3, which is about 260% that of the bilayer P­(VDF–HFP)/PMMA composite (∼3.9 J/cm3), is achieved at 600 kV/mm. This work offers a facile strategy to achieve dielectric composites with high breakdown strengths, which is illuminating for the design of high-voltage energy-storage capacitors.